Abstract Detail

Tempo and mode of plant evolution on limestone karst in Guangxi, China - Insights from phylogenetics of Primulina (Gesneriaceae).

The limestone karst landscape in Guangxi, China harbors extremely high-level of biodiversity and endemism. It has long been suggested that that the unique geological features of karst topography in Guagnxi might have driven high speciation rates of plants there. Primulina(Gesneriaceae),a monotypic genus recently reircumscribed to include Chirita sect. Gibbosaccus, Chiritopsis, and Wentsaiboea,is one of the most representative limestone plant taxon inhabiting this area.Previously, an allopatric speciation mode has been proposed to explain the highs pecies diversity in Primulina, andgeological events were suggested to be associated with the diversification. Inthis study, we present phylogenetic analyses of 147 samples (97 species) of Primulina and allied genera using ITSand trnL-F sequences. The speciation mechanisms of Primulina were inferred by molecular dating and analysis of geographic distributions. Within the highly supported monophyletic Primulina, species distributed in geographical proximity are also phylogenetically closely related, suggesting that geography should have played a crucial role and species were highly likely to have diverse dallopatrically. Divergence time estimates reveal a crown age of Primulina originated at ca. 23MYBP and the basal Primulina clades later diversified within a narrow time-span ranging from 19.53 MYBP to 18.37 MYBP. Combined with the results of phylogenetic and geographic analyses, the delayed and rapid accumulation of the extant Primulina species after the origin of this genus implies an early radiation, likely driven by repeated allopatric speciations associated with ancient geological events that have characterized the unique geology of the limestone karst in Guangxi,China.